1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device and fabricating method thereof.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts are being made to study and develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
FIG. 1 is a perspective view of a liquid crystal panel of an LCD device according to the related art. As shown in FIG. 1, a liquid crystal panel 1 includes an upper substrate 10, a lower substrate 20 and a liquid crystal layer 40. The upper substrate 10 is referred to as a color filter substrate that includes a color filter pattern 14, a black matrix 12 between the color filter patterns 14, a common electrode 18 on both the color filter pattern 14 and the black matrix 12. The lower substrate 20 is referred to as an array substrate that includes a data line 24 and a gate line 22 that cross each other and define a pixel region P. A pixel electrode 36 and a thin film transistor Tr as a switching element are positioned in each pixel region P. Thin film transistors Tr, which are disposed adjacent to where the data lines 24 and the gate lines 22 cross, are disposed in a matrix form on the lower substrate 20.
FIG. 2 is a cross-sectional view of a liquid crystal panel according to the related art. As shown in FIG. 2, a liquid crystal panel 40 includes lower and upper polarizing films 50 and 52 disposed on the outer surfaces of the lower and upper substrates 20 and 10, respectively. Although not shown in FIG. 2, a backlight unit including a lamp and at least one optical sheet are disposed below the lower polarizing film 50.
FIGS. 3A to 3D are cross-sectional views of the fabricating method of a color filter substrate according to the related art. As shown in FIG. 3A, a metal or a resin is deposited on a substrate 10 and patterned to form a black matrix 12. The black matrix 12 prevents light leakage and shields the channel portion of a thin film transistor from incident light.
As shown in FIG. 3B, a red color resist is deposited over the substrate 10 having the black matrix 12 by a coating process, such as spin coating, to form a red resist layer 13. Then, the red resist layer 13 is exposed to light through a mask 15 having a light-transparent portion and a light-blocking portion. The red color resist is a negative type resist.
As shown in FIG. 3C, since the red color resist is a negative type resist, the light-exposed portion of the red resist layer 13 (in FIG. 3B) remains while the light-blocked portion of the red resist layer 13 (in FIG. 3B) is removed so that a red color filter pattern 14a is formed. Then, the red color filter pattern 14a is cured.
In FIG. 3D, green and blue color filter patterns 14b and 14c are similarly formed. Then, a transparent conductive material is deposited over the color filter patterns 14 to form a common electrode 18. The transparent conductive material can be indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). An over-coat layer 16 can be formed between the common electrode 18 and the color filter patterns 14. The over-coat layer 16 planarizes the surface of the color filter patterns 14 on the substrate 10.
The color filter substrate fabricated through the above-mentioned processes is attached to an array substrate so that the inner surfaces of the substrates face each other. Then, a liquid crystal material is injected between the two substrates so that a liquid crystal panel is formed. Subsequently, upper and lower polarizing films are attached on outer surfaces of the liquid crystal panel, respectively.
FIG. 4 is a cross-sectional view of a color filter substrate, on which a polarizing film is attached, according to the related art. As shown in FIG. 4, a polarizing film 52 is attached on an outer surface of a color filter substrate 11 having a black matrix 12, red color filter pattern 14a, green color filter pattern 14b, blue color filter pattern 14c and a common electrode 18. Since the polarizing film 52 is attached on an outer surface of the color filter substrate 11, undesired light coming from the color filter patterns 14 is not blocked by the polarizing film 52. In other words, light going through the color filter patterns 14 is scattered by pigments dispersed in the color filter patterns 14 so that the scattered light leaks through the polarizing film 52. Therefore, polarizing efficiency of the LCD device is reduced.
Because the polarizing film 52 has a thickness of more than 200 micrometers (um), the polarizing film 52 causes the LCD device to have a thicker profile, which is contrary to the desired characteristic of the thin profile. Additionally, since the polarizing film 52 is formed by a film-stretching method, the polarizing film 52 is weak to heat and moisture. Thus, the performance of the liquid crystal panel can be adversely affected by heat and moisture. Further, the polarizing film 52 makes the liquid crystal panel inflexible because it includes a hard-type base film supporting a polarizing layer and an adhesive layer.